This invention relates to liquid ring vacuum pumps and compressors, and more particularly to constructions for such products which increase the number of parts that can be used in more than one product configuration. For ease of reference, the term xe2x80x9cpumpxe2x80x9d or xe2x80x9cpumpsxe2x80x9d is generally used herein as a generic term for both pumps and compressors.
Liquid ring pumps are typically designed so that a single pump design can serve a number of markets. Accordingly, the same basic pump may be used for different applications such as chemical processing, general industrial markets, and so on. Generally, chemical and petrochemical process applications require higher discharge and hydrostatic test pressure (i.e., liquid leakage pressure) capabilities and the use of special mechanical seals. These requirements are often not so stringent in general industrial applications. For example, in the chemical processing industry differential pressures to 30 psig and hydrostatic test pressures to 225 psig are common requirements. In comparison, for general industrial pumps the differential pressure capability required is typically about 15 psig and hydrostatic test is about 75 psig. Also, chemical industry pumps may have to meet certain industry specifications such as those set by the American Petroleum Institute or the Engineering Equipment and Materials Users Association.
Because a liquid ring pump may be needed for any of these markets, overall design is often based on meeting specifications for the more demanding chemical process applications. The resulting design is xe2x80x9coptimalxe2x80x9d for chemical applications, but may be xe2x80x9cover-designedxe2x80x9d for general industrial applications. Pumps of the type shown in Dudeck et al. U.S. Pat. No. Des. 294,266 (also known as the xe2x80x9cSCxe2x80x9d type of pump available from The Nash Engineering Company of Trumbull, Connecticut) are an example of this type of known pump design. To meet the more stringent requirements of chemical process applications, these pumps have removable bearing brackets to facilitate access to the mechanical seals. The seals are also provided with an external flush to cool the seal and help reduce erosive damage to the seal components. Features such as these are often not necessary for less demanding general industrial applications. Accordingly, the SC design may be a more costly one than is needed for such less demanding installations. On the other hand, it is also costly to provide completely separate designs that have been optimized for each possible application.
(It should be noted here that the SC pumps also use gas scavenging technology of the type shown in Schultze et al. U.S. Pat. No. 4,850,808, which is hereby incorporated by reference herein in its entirety.)
In view of the foregoing, it is an object of this invention to provide liquid ring pumps that can economically meet the requirements of several different types of service without all parts of the pump having to be entirely customized to each type of service.
It is another object of this invention to provide simplified lubrication of seals which can be used in at least some liquid ring pumps.
These and other objects of the invention are accomplished in accordance with the principles of the invention by providing liquid ring pumps having at least several major components that can be used or easily adapted for use in pumps having either of at least two significantly different designs, each of which is adapted to meet a respective one of two significantly different sets of service requirements. For example, although two different pumps may have such variations as different shaft diameter and shaft length between bearings, the two pumps may have several common rough parts such as the rotor, head, cone, and lobe, and may have common finished parts such as the lobe. To accomplish this in the case of the head, for example, that part may be cast with sufficient material in the shaft area so that this material can be machined out either for a relatively large shaft (for a higher pressure pump) or for a relatively small shaft plus a bearing (for a lower pressure pump). Similarly, in the case of the cone, that part may be cast with enough material in the shaft area so that it may be machined out either for the larger shaft or for a relatively small shaft plus mechanical seal components.
The pumps of this invention may also be constructed with features that simplify the provision and lubrication of seals, especially for pumps with less stringent seal requirements. For example, at one end of the pump the seals may be located inside the cone of the pump where they can be lubricated by the flow through the above-mentioned gas scavenging structure associated with the cone. At the other end of the pump, the rotor shroud may be perforated to facilitate a flow of liquid from the liquid ring to and past the seals at that end.
Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments.